On Mon, Apr 28, 2014 at 2:08 AM, Marek Vasut marex@denx.de wrote:
On Sunday, April 27, 2014 at 05:29:29 PM, Chen-Yu Tsai wrote:
On Sun, Apr 27, 2014 at 11:25 PM, Ian Campbell ijc@hellion.org.uk wrote:
On Sat, 2014-04-26 at 20:28 +0200, Marek Vasut wrote:
On Friday, April 18, 2014 at 08:05:50 PM, Ian Campbell wrote:
From: Jens Kuske jenskuske@gmail.com
The GMAC module in Allwinner sunxi SoCs seems to have problems with burst lengths > 8.
Is there any explanation for the problems please ?
Jens or Wens, can you answer this?
IIRC, with burst lengths > 8, GMAC doesn't work, no ping, no DHCP. I don't remember if it was TX or RX that suffered, or even both.
Hope this clarifies things a bit.
No, it does not at all, sorry. What you describe are symptoms, but what I want to know is what is the root cause of those symptoms. You did not explain that.
I can not offer much more explanation. The value was hardcoded in Allwinner's code. The datasheets don't offer much, except this line might be related:
(DMA) Descriptor architecture, allowing large blocks of data transfer with minimum CPU intervention; each descriptor can transfer up to 4 KB data.
Also probably related:
4KB TX FIFO for transmission packets and 16KB RX FIFO for reception packets.
I'm not an expert in hardware. We could ask Allwinner, but given past inquiries from the linux-sunxi community, I'd say getting a reply on hardware specifics is unlikely to happen.
So my guess is that this is limited by the DWMAC IP Allwinner licensed from Synopsys.
Cheers ChenYu